The present invention is directed to a method of base stabilization for use in the construction or reconstruction of roadways. More specifically, the present invention is directed to an improved method of increasing the strength and decreasing the permeability of the base course of a roadway through the addition of a unique combination of stabilizers to base materials.
A roadway is typically formed of at least four distinct courses, a subbase course, a base course, a binder course, and a surface course. Each of these courses serves a distinct and important role in the overall stability and durability of the roadway.
Stability, as used in the roadway construction industry, refers to the ability of a roadway or asphalt paving composition to resist deformation from imposed loads. If the materials needed for the roadway construction do not provide enough “stability” to satisfy the roadway design requirements, the materials may be modified with specific stabilizing agents to enhance certain qualities, such as strength and flexibility, or to decrease other qualities, such as permeability.
A specific stabilizing agent or “stabilizer” is selected to enhance a specific property. For example, stabilizers such as fly ash, Portland cement, and lime are known to increase the strength of pavement materials. Accordingly, these stabilizers are commonly added when additional strength is need.
Similarly, stabilizers such as asphalt emulsion are known to increase the flexibility and decrease the permeability of pavement materials. Accordingly, these stabilizers are used when increased flexibility or decreased permeability is desired.
The base course of a roadway, which is formed between the subbase course and the pavement course, is designed to provide strength and support to the roadway structure. The base course is typically formed of crushed stone, slag or similar materials and may include both a subgrade layer and a pavement base layer. If the base materials do not provide enough strength to accommodate the desired roadway design, the base materials are modified with stabilizers such as fly ash and Portland cement, to enhance their overall strength.
Unfortunately, a stabilizer such as asphalt emulsion, which is known to increased flexibility and decreased permeability of pavement materials, is as also understood to reduce the strength of these materials. Therefore, although asphalt emulsion is typically used to stabilize the pavement course, binder course and even a black base layer, it is not used in the stabilization of a base course layer.